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MagMueller
92 lines
3.7 KiB
Python
92 lines
3.7 KiB
Python
"""Tests for MCP tool annotations on the `browser-use --mcp` surface (#5239).
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The MCP tool catalogue used to ship without any `annotations`, so clients that
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gate tool execution on MCP hints (e.g. Codex CLI with `approval_policy=never`)
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auto-cancelled even clearly read-only calls like `browser_get_state`.
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Read-only tools must advertise `readOnlyHint=True`; every state-changing tool
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must NOT advertise it. `browser_extract_content` is deliberately excluded from
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the read-only set: it dispatches the `extract` action through `Tools.act()`
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with a FileSystem handle and can write extraction artifacts.
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"""
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import mcp.types as types
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import pytest
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from browser_use.mcp.server import BrowserUseServer
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# Tools whose handlers only read state (see BrowserUseServer._get_browser_state,
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# _get_html, _screenshot, _list_tabs, _list_sessions). Everything else mutates
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# browser/session state and must never carry readOnlyHint=True.
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EXPECTED_READ_ONLY_TOOLS = frozenset(
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{
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'browser_get_state',
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'browser_get_html',
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'browser_screenshot',
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'browser_list_tabs',
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'browser_list_sessions',
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}
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)
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@pytest.fixture
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def server() -> BrowserUseServer:
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return BrowserUseServer()
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def _is_read_only(tool: types.Tool) -> bool:
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return tool.annotations is not None and tool.annotations.read_only_hint is True
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async def _list_tools(server: BrowserUseServer) -> list[types.Tool]:
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handler = server.server.get_request_handler('tools/list')
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assert handler is not None, 'tools/list handler is not registered'
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list_result = await handler.handler(None, types.PaginatedRequestParams()) # type: ignore[arg-type]
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assert isinstance(list_result, types.ListToolsResult), f'expected ListToolsResult, got {type(list_result).__name__}'
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assert len(list_result.tools) > 0, 'tools/list returned an empty catalogue'
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return list_result.tools
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async def test_read_only_tools_advertise_read_only_hint(server: BrowserUseServer) -> None:
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"""Every genuinely read-only tool must carry annotations.readOnlyHint=True."""
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tools = await _list_tools(server)
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by_name = {tool.name: tool for tool in tools}
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missing_tools = EXPECTED_READ_ONLY_TOOLS - by_name.keys()
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assert not missing_tools, f'expected read-only tools missing from tools/list: {sorted(missing_tools)}'
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unannotated = sorted(name for name in EXPECTED_READ_ONLY_TOOLS if not _is_read_only(by_name[name]))
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assert not unannotated, (
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f'read-only tools missing readOnlyHint=True: {unannotated}. '
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f'Clients that gate on MCP annotations (e.g. Codex approval_policy=never) cancel unannotated calls.'
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)
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async def test_mutating_tools_never_advertise_read_only_hint(server: BrowserUseServer) -> None:
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"""No state-changing tool may claim to be read-only.
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A new tool that carries readOnlyHint=True must be consciously added to
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EXPECTED_READ_ONLY_TOOLS after checking its handler really only reads.
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"""
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tools = await _list_tools(server)
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mislabeled = sorted(tool.name for tool in tools if tool.name not in EXPECTED_READ_ONLY_TOOLS and _is_read_only(tool))
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assert not mislabeled, f'state-changing tools wrongly advertise readOnlyHint=True: {mislabeled}'
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async def test_unknown_tool_is_reported_as_mcp_error(server: BrowserUseServer) -> None:
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"""Unknown tool calls must not be returned as successful MCP results."""
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handler = server.server.get_request_handler('tools/call')
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assert handler is not None, 'tools/call handler is not registered'
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result = await handler.handler(
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None, # type: ignore[arg-type]
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types.CallToolRequestParams(name='does_not_exist', arguments={}),
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)
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assert isinstance(result, types.CallToolResult)
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assert result.is_error is True
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assert len(result.content) == 1
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assert isinstance(result.content[0], types.TextContent)
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assert 'Unknown tool: does_not_exist' in result.content[0].text
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